1. Field of the Invention
The present invention relates to a cooling apparatus boiling and condensing refrigerant, capable of absorbing heat generated from high-temperature medium such as a heating body of semiconductor devices or electric devices, to cool the high-temperature medium.
2. Description of Related Art
There have been known cooling apparatuses boiling and condensing refrigerant, for cooling heat generated from a heating body as high-temperature medium. Among those known cooling apparatuses, as disclosed in JP-A-56-147457, there is a cooling apparatus capable of preventing a flooding of a ascending refrigerant which has been boiled and vaporized and liquid refrigerant which has been cooled in a radiator and is returning to a refrigerant tank, within the apparatus, i.e., a phenomenon in which both collide with each other, to perform a heat exchanging operation efficiently.
The cooling apparatus disclosed in JP-A-56-147457 includes a refrigerant tank for containing a refrigerant to be boiled and evaporated by heat generated by a heating body, an inflow passage having a substantially uniform diameter communicating with the refrigerant tank, a radiator having a plurality of radiating passages communicating with the inflow passage, and an outflow passage through which the refrigerant condensed and liquefied in the radiator is returned to the refrigerant tank.
According to this cooling apparatus, in a normal operation (an amount of radiating heat is small), bubbles of the refrigerant blow up and the refrigerant flows through the inflow passage in a gas-phase to transfer heat. That is, the gas-phase refrigerant comes into direct contact with walls defining the radiating passages so that heat is transferred directly to the walls (condensation heat transfer).
However, as the amount of radiating increases, bubbles of the refrigerant blow up greatly and part of the refrigerant flows in a liquid-phase through the inflow passage, so that heat is transferred by both the gas-phase and the liquid-phase refrigerant. The liquid refrigerant transfers heat not by condensation but by forced convection, i.e., by the heat transfer of the liquid refrigerant with the wall of the radiating passages. The efficiency of heat transfer by forced convection is {fraction (1/10)} to {fraction (1/20)} of that of heat transfer by condensation.
Since the inflow passage communicating with the refrigerant tank of the cooling apparatus disclosed in JP-A-56-14757 has a substantially uniform diameter, a relatively large amount of liquid refrigerant flows into the radiating passages, which results in a problem that the radiating characteristics of the whole cooling apparatus deteriorates remarkably.
Further, since the inflow passage communicating with the refrigerant tank of the cooling apparatus disclosed in JP-A-56-147457 has a substantially uniform diameter, the flow resistance in the inflow passage is relatively low. Therefore, the gas-phase refrigerant which rises up and reaches the inflow passage is likely to stay at an end portion of the inflow passage apart from the inlet of the inflow passage and hence the end portion of the inflow passage is heated at a high-temperature. Even if the cooling apparatus is provided with a plurality of radiating passages, the temperatures of portions of the radiating passages, which are away from the end portions are relatively low and hence heat cannot be radiated efficiently. Consequently, the radiating performance of the cooling apparatus is low as compared with the size of the radiator.
Accordingly, it is a first object of the present invention to provide a cooling apparatus capable of preventing the radiating performance from deteriorating.
A second object of the present invention is to provide a cooling apparatus capable of suppressing the liquid-phase refrigerant (liquid refrigerant) from flowing into radiating passages.
A third object of the present invention is to provide a cooling apparatus having a radiator provided with a plurality of radiating passages capable of radiating heat at substantially equal radiating rates, respectively.
A fourth object of the present invention is to provide a cooling apparatus having a radiator provided with a plurality of radiating passages, and capable of distributing a refrigerant at substantially equal flow rates to the radiating passages.
According to an aspect of the present invention, a radiator is provided with an adhesion amount reducing means for reducing an amount of the liquid refrigerant flowing from a refrigerant tank and adhering to an inner surface of radiating passage so that an area for heat transfer by condensation in the radiating passages can be increased.
According to another aspect of the present invention, a cooling apparatus has a radiator provided with an inflow passage into which the gas-liquid mixed refrigerant flows from a refrigerant tank, an outflow passage for sending out the refrigerant tank to the refrigerant tank, and a radiating passage communicating the inflow passage with the outflow passage, the inflow passage having a large-diameter portion having a diameter and a small-diameter portion having a diameter smaller than the diameter of the large-diameter portion, which are formed alternatively in a direction where the gas-liquid mixed refrigerant flows.
When an amount of radiating heat is large, the refrigerant blows up bubbles in the refrigerant tank and both the gas-phase and the liquid-phase refrigerant flow into the inflow passage. The small-diameter portion formed in the inflow passage in the direction where the refrigerant flows suppresses the liquid refrigerant flowing into the adjacent radiating passage. The liquid refrigerant dammed by the small-diameter portion is returned into the refrigerant tank. Since the amount of the liquid refrigerant flowing into the radiating passage is reduced by the small-diameter portion, an area for heat transfer by condensation can be increased.
The refrigerant tank may be provided internally with vapor passages through which the gaseous refrigerant having been vaporized by heat transferred from a high-temperature medium and the liquid refrigerant ascend, and a condensed liquid passage through which the liquid refrigerant having been cooled and condensed in the radiator descends. Therefore, the flooding the flooding in which the boiling refrigerant and the condensed refrigerant collide with each other and can be prevented.
According to another aspect of the present invention, a cooling apparatus has a radiator provided with a liquid refrigerant returning portion having an inflow return chamber having a small-diameter opening formed integrally with a refrigerant tank outlet and having a diameter smaller than an inner diameter of the radiator, for damming liquid refrigerant by the small-diameter opening, and a return passage communicated with an outflow return chamber to return the dammed liquid refrigerant to the refrigerant tank.
The lowermost portion of the small-diameter opening may be higher than a bottom surface of the inflow return chamber of the liquid refrigerant returning portion by a predetermined height. Therefore, the liquid refrigerant of the gas-liquid mixed refrigerant having flowed through the refrigerant tank outlet, which boils up from the refrigerant tank, can be dammed efficiently.
The small-diameter opening may be formed by punching into a substantially elliptic or rectangular shape. Therefore, the liquid refrigerant or the gas-liquid mixed refrigerant having passed the refrigerant tnaky outlet can be dammed efficiently so that an effective area of the radiator can be increased, and the radiating performance can be improved.
Each bottom surface of the radiating passages may be inclined downward from the refrigerant outlet toward the refrigerant tnak inlet to return the condensed liquid refrigerant from the radiating passages toward the refrigerant tank smoothly. Therefore, the amount of the condensed liquid refrigerant staying on the bottom surfaces of the radiating passages is reduced, an area for heat transfer by condensation can be increased and hence the gaseous refrigerant can be condensed efficiently.